Jersey City Police Chief Robert Cowan is alleging that Mayor Steve Fulop planned to snarl traffic outside of the Holland Tunnel the same month he announced plans to sue the Port Authority for $400 million.

In an eight-page letter Cowan submitted to the city clerk, the chief says that at a November 2013 meeting with Fulop, Cowan was directed to conduct traffic stops "without sufficient reason" that Cowan says would have caused traffic jams "on the streets of New York City and back traffic up into the Holland Tunnel," the letter reads.

The chief says he objected because of the plan's "illegality" and that it was ultimately canceled. A few days later, Cowan alleges, Fulop told him to conduct traffic stops at "Old Colony Road and Port Jersey Blvd." near the Global Container Terminal owned by the Port Authority.

In the letter, which Cowan says is his attempt to address "the real reasons" Fulop is demoting him, the chief alleges that when he pointed out the "very heavy volume of truck traffic" heading in and out of the terminal, Fulop was irate.

Fulop, a Democrat, "told me he wanted it done at Old Colony and he was not going to have negotiations with me," the letter reads.

There is a Colony Road that intersects with Port Jersey Boulevard. Asked to clarify, Stangler said Cowan told her Old Colony Road is correct.

Police followed through with that operation, which caused hours of gridlock inside the terminal on Nov. 19 and led to accusations by the Global Terminal chief that Fulop was seeking to punish the Port Authority. At the time, city spokeswoman Jennifer Morrill said the traffic stops were unrelated to the lawsuit, which alleges the Port Authority doesn't pay its fair share of property taxes.

Cowan says in his letter that when he saw the traffic caused by the truck inspections, he called off the operation.

Cowan also alleges that Fulop confronted him at an Atlantic City casino on Nov. 20 during the New Jersey State League of Municipalities convention, telling Cowan he wanted another traffic stop operation and reminding the chief he serves at Fulop's "discretion."

A city official forwarded a Feb. 20, 2014 email from Cowan that includes a memo saying the Port Jersey traffic stops were part of a citywide traffic safety initiative.

City spokeswoman Jennifer Morrill said the city and Fulop "have always acted in 100 percent accordance with the law to protect Jersey City residents."

"Cowan is obviously upset about his demotion but the decision to remove him as police chief was in the best interest of the police department and Jersey City," Morrill said in an email.

Last month, Fulop announced that he plans to demote Cowan, who was sworn in as head of the roughly 800-officer police force on Oct. 1. The move, which Fulop said comes in part because of a number of legal actions filed against the chief, is unprecedented, city officials have said. The demotion becomes official Tuesday.

Cowan requested a hearing in front of the City Council, which could reverse Fulop's decision, but Fulop allowed only a meeting between himself, Cowan, Cowan's attorney, Public Safety Director James Shea and a city attorney. That meeting was Thursday.

Cowan's letter ends with a threat to sue Fulop and the City Council.

Council President Rolando Lavarro said he hasn't reviewed Cowan's letter and has no comment.